The radius of a right circular cylinder is increased by $50 \% .$ Find the percentage increase in volume (in $\%$)?

$A$ hollow spherical shell is made of a metal of density $4.9 \, g/cm^3$. If its internal and external radii are $10 \, cm$ and $12 \, cm$ respectively,find the weight of the shell. (Take $\pi = 3.1416$) (in $gm$)

$A$ circular road runs round a circular ground. If the difference between the circumferences of the outer circle and the inner circle is $66 \, m$,the width of the road is ....... $m$.

$A$ playground is in the shape of a rectangle. $A$ sum of ₹ $1,000$ was spent to make the ground usable at the rate of $25$ $paisa$ per $m^2$. The breadth of the ground is $50\, m$. If the length of the ground is increased by $20\, m$,what will be the expenditure in rupees at the same rate per $m^2$?

Find the area of an isosceles right-angled triangle whose hypotenuse is $8\, cm$.

$A$ bed of roses is shaped as shown in the figure below. In the centre is a square and on each side there is a semi-circle. The side of the square is $21 \, m$. If each rose plant needs $6 \, m^{2}$ of space,then the number of plants in the bed is?